Reduction of hematite (Fe2O3) to wüstite (FeO) by carbon monoxide (CO) for chemical looping combustion

• TGA reduction of hematite (Fe2O3) in CO (5–20%) was conducted at temperatures from 750 to 900 °C.
• A single reaction scheme was applied to the reduction data.
• The reaction is first-order.
• The reaction rate increases with temperature and CO concentration.

Thermogravimetric analysis (TGA) of the reduction behavior of hematite by using continuous streams of 5%, 10%, and 20% CO concentrations in N2 was conducted at temperatures ranging from 750 to 900 °C over ten cycles. The reduced hematite was then oxidized using dry air. The rate of reduction was determined by the sample weight loss. Analysis of the data indicated that the reduction behavior can be described by single rate-determining step and it was controlled by the chemical reaction at the particle surface. The mass spectroscopy analysis of product gas indicated that no carbon deposition was found when operating at these temperature ranges (750–900 °C). The analysis of reduction showed that two reduction steps (Fe2O3 → Fe3O4, Fe3O4 → FeO) proceed simultaneously. The activation energy was estimated to be 19.0 ± 0.14 kJ/mole.